A 48-year-old man with a newly diagnosed acute myeloid leukemia developed purpuric rash on day 6 after chemotherapy. Skin biopsy on day 8 demonstrated Grover disease. Triamcinolone treatment started on day 10 with subjective improvement on day 15. Initial FDG PET/CT on day 12 demonstrated rarely seen diffuse skin uptake that was interpreted as technical artifact and repeated on day 16. Accurately reviewing both PET and CT imaging would prevent confusion between diffuse cutaneous hypermetabolic activity and a technical artifact. Grover disease usually affects the trunk and may be related to the elimination of chemotherapy agents by sweating.